Don't Let Pigweed Hitch a Free Ride

Don't Let Pigweed Hitch a Free Ride

Beware of Trojan horse on used equipment 

When buying and transporting used equipment, pigweed has been known to tag along for the ride. Farmers are unaware of the danger until Palmer amaranth pops up in fields a season later. 

A prolific tiny seed can find many places to hide on combines, semis or other equipment. Cleaning success rates are an open question, but the potential of spreading Palmer amaranth via seed transport is a threat farmers must keep in mind—particularly when the equipment comes from the South where Palmer amaranth risks are a near certainty.

“At the least, farmers should blow out purchased equipment with air and clean out every nook as best as possible,” advises Kevin Bradley, weed scientist, University of Missouri Extension. “In meetings when I’ve warned Midwest farmers about pigweed transport potential, there have been multiple times when a farmer came to me afterward and asked, ‘I’m supposed to pick up a combine down in Arkansas. Should I clean it out?’”

A weed beast with few peers, Palmer amaranth can jump 2" to 3" daily and become uncontrollable in 24 hours. Controlling pigweed post-emergence is extremely difficult, and ignoring an outbreak swamps farmland. 

Palmer amaranth seed can survive four to five years in soil and remain viable. Bradley suspects Palmer amaranth stowaways on equipment—free from moisture or bug pressure—could last much longer.

From personal experience, he knows the dangers and consequences of transporting Palmer amaranth seed. He harvested a Palmer amaranth site at the end of 2013 and then changed locations to complete a few more trials at his research farm in Columbia, Mo., which had never been afflicted with Palmer amaranth. In the spring of 2014, Bradley walked his Columbia acreage and found Palmer amaranth. “There is no other conclusion: We transplanted the Palmer with our own combine. Sure, it’s only two or three plants at first, but it spreads incredibly fast,” he says.

Midwest weed scientists are trying to educate growers about pigweed. “If a grower is unsure about Palmer or any weed, they should contact us immediately and send samples in if necessary. If the weed is confirmed as Palmer, then it’s off to the races. We need to get rid of it as quickly as possible and pay close attention to that field for the rest of the year.”

Some Midwest states are finding Palmer amaranth sneaks in as a result of feed, usually a cottonseed source, or contaminated hay or straw. If a product comes out of the South, it’s conducive to resistant Palmer amaranth transport. Christy Sprague, weed scientist, Michigan State University Extension, first began seeing Palmer amaranth in fields where dairy manure had been applied. “Our speculation pointed to cotton gin trash,” she says. “Trucks come up from the South, and the cottonseed can be clean, but the overall gin trash may contain pigweed seed, and it only takes a small amount.”

Palmer amaranth isn’t widespread in Michigan, but Sprague continues getting more calls from farmers. “We’ve got several counties hit with Palmer amaranth, but it hasn’t expanded to the extent of the pigweed spread in Indiana. Fortunately, we haven’t had the huge explosion we were expecting when we first found it in 2010.”

Bradley emphasizes vigilance for Midwest producers: “Farmers have to be on the lookout. We’re already ground zero for resistant water hemp, and we want to delay Palmer’s spread as long as possible.” 

Back to news


Spell Check

No comments have been posted to this News Article

Corn College TV Education Series


Get nearly 8 hours of educational video with Farm Journal's top agronomists. Produced in the field and neatly organized by topic, from spring prep to post-harvest. Order now!


Market Data provided by
Brought to you by Beyer